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Published June 20, 1994 | Submitted
Book Section - Chapter Open

Long-Term Monitoring of the Accreting Pulsar GX 1+4


We present preliminary results from two years of GRO/BATSE hard X‐ray (20–100 keV) monitoring of the ∼120 s accretion‐powered pulsar GX 1+4. Daily pulse frequency measurements from 1991 April to 1993 September show an average spin‐down of ḟ≊−5×10^(−12) s^(−2), with increases in the spin‐down rate during high‐luminosity intervals. The 20–100 keV pulsed flux spectrum for the interval TJD 8393–8406 is fit by a power‐law index of 2.56±0.04. Optical spectroscopy of the suggested red giant companion V2116 Oph taken during the 1993 September X‐ray outburst from GX 1+4 show considerably strengthened emission line features, supporting the association.

Additional Information

© 1994 American Institute of Physics. Published online 20 June 1994. We acknowledge the significant contributions to this work by the entire BATSE instrument team at NASA/MSFC. We also thank F. K. Lamb for useful comments. This work is supported in part by NASA grants NAGW-1919, NAGW-2920, and NAG 5-1458, as well as a Lee A. DuBridge fellowship to L.B. funded by the Weingart Foundation.

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